Double parallel plane magnetron



Aug. 11, 1953 P. l. CORBELL ,6 8,8

DOUBLE PARALLEL PLANE MAGNETRON Filed Dec. 2. 1949 2 Sheets-Sheet l 55 [IVE/V701? Q OQ QvJ-ed Aug. 1953 P. l. CORBELL 2,648,800

DOUBLE PARALLEL PLANE MAGNETRON Filed Dec. 2, 1949 2 Sheets-Sheet 2 I \x. in

Patented Aug. 11, 1953 DOUBLE PARALLEL PLANE MAGNETRON Paul I. Corbell, Cedar Rapids, Iowa, assignor to Collins Radio Company, Cedar Rapids, Iowa, a

corporation of Iowa Application December 2, 1949, Serial No. 130,819

3 Claims.

This invention relates in general to electronic discharge devices and in particular to a magnetron tube.

As the state of the electronic art has developed, it has been found desirable to work at higher and higher frequencies. Because the physical dimensions of an electronic device affect frequency, smaller and smaller tubes have been developed to increase the frequency. Another way of increasing the frequency of the electronic device is to place the capacitance and inductance in the device itself. Stated otherwise, where it used to be considered necessary to add inductive and capacitive reactance in an external circuit, it is now feasible to design the elements of a tube so that the inductance and capacitance are inherent in the cathode, grid, and anode structures. The resnatron tube and the magnetron tube are examples of such tubes. This invention relates in particular to a new kind of magnetron.

The cathode of a magnetron tube must be heated to a temperature sufficient to cause thermal emission of electrons. In the ordinary magnetron tube only one surface of the cathode furnishes electrons to the anode and thus the maximum emission from the cathode is not used.

It is an object of this invention, therefore, to provide a parallel plane magnetron which has an anode structure at either side of the cathode to facilitate a more useful utilization of the emissions of the cathode.

A further object is to provide a pair of anodes adjacent to the cathode so that the magnetic field may be more efiiciently utilized.

Still another object of this invention is to provide a pair of anodes closely spaced to a common cathode so that an increase in power may be obtained over a single anode tube with the addition of the second anode.

Further objects, features, and advantages wi become apparent from the following description and claims when read in the light of the drawings; inwhich:

Figure 1 is a top plan view of the magnetro tube of this invention;

Figure 2 is a sectional view taken along line 22 in Figure 1; and,

Figure 3 is an exploded perspective viewof the magnetron showing the internal spatial relationships among the various component parts. Referring to Figure 3, a hollow cylindrical member I has an annular pole piece I I attached to the inner wall 12 near the mid-point. Extending through the walls of the member Iii are three .conductor supports AS shown in Fi ure 1 those supports are spaced equidistant about the cylindrical member H3. The conductorsupports I3 pass through the wall of thecylindrical member Ill and a seal I 6 prevents the pas-'- sage of air through the openings in the member It in a well known manner.

At the inner ends I! of the conductor-support members is connected a cathode support ring I8 which is held in a predetermined concentric relationship with the inner wall of the cylindrical member by the support members I3.

A pair of cover discs I9 and 2 I, fit over the open ends of the cylinder I B. The top plate I9 is formed with a central opening into which a short hollow ring 22 is received. The inner end of the ring 22 does not extend through the top plate I9 but is maintained in abutting engagement with a second hollow ring 23. The ring 23 extends downwardly and is connected to a second annular pole piece 24. The pole piece 24 is formed with a central opening 25 which extends more than half-way through the pole piece. The ring 23 is formed with radial holes 2! for evacuating the top portion of the tube.

The bottom cover member 2| is also formed with a central opening through which extends a tube 28. A magnetic conducting member 29 surrounds the tube 28 and fits in abutting engagement with a shoulder 3! of the bottom plate 2|. A second magnetic-conducting member 32 extends downwardly from the pole piece 24 to complete the magnetic circuit. A plurality of radial openings 33 are formed in the magneticconducting member 32, to allow the gases within the confines of the magnetron to be removed by a vacuum pump connected to the tube 28. The pole piece 24' is of a substantially disc shape and its outer edge 34 is equidistant from the pole piece II so that flux distribution between the two will be symmetrical.

A magnetic circuit, not shown, connects the magnetic-conducting member 29 with the pole piece II in a manner well known to the art. Generally, an electrical conductor is wound about the magnetic material to produce the desired flux;

Extending axially into the upper end of the tube 22 is a conductor 36. Three smaller conductors 3'? extend radially from the conductor 38 and through openings 38 provided in the pole piece 24 for that purpose. The outer ends :39 are connected to a second cathode holding ring 45. The conductors 31 also act as mechanical support for the ring 4 I.

Between the cathode holding rings I8 and 4-.I is the cathode '42.

The upper end of the tube 22 is closed by a cover 43 which is sealed thereto with a glass to metal seal. The conductor 36 passes through the cover 43 and the junction is airtight.

Extending downwardly from the top cover I9 is a first anode 44. The anode is formed with a plurality of downwardly-extending fingers 46. The lower ends 41 of the fingers 46 are within close proximity to the cathode and the electrons emitted from the cathode flow toward the anode.

A second anode structure 48 extends upwardly from the bottom cover 2 I. It is also formed with fingers 49 which are in close proximity to the opposite side of the cathode 42. Electrons also fiow from the cathode toward the lower anode 48.

A suitable low voltage is supplied to the oathode 42 through the conductors I1 and 31. This voltage heats the cathode to an emission temperature. The conductors H and 31 are alternately spaced so that the current distribution in all parts of the cathode will be symmetrical.

A relatively high direct potential is applied through the conductor 36 between the cathode 42 and the anodes 44 and 48. This direct potential is the accelerating potential between the cathode and anodes. The anodes are generally grounded and a negative potential with respect to ground is furnished to the cathode. Thus the covers l9 and 2! are at ground potential. The battery B shown in Figure 2, which has its positive side connected to the cover l9 and its negative side connected to the conductor 36, supplies a direct potential between the anode and cathode. The cover I9 is electrically connected to the upper and lower anodes and the lead 36 is electrically connected to the annular cathode. Sometimes, however, it is desirable to operate the anodes at diiferent direct potentials. This may be done by insulating the top anode l9 from the lower anode 2|.

The cathode holding rings I8 and 4! do not substantially affect the magnetic field between the pole pieces H and 24 because they are of nonmagnetic material, such as copper, for example.

The magnetic field tends to move electrons in a circular path in a plane at right angles to the lines of flux. Thus, the electrons emitted from the cathode will have a velocity component which is parallel to the anode fingers and the cathode due to the combined action of the electrostatic and the magnetic fields. As the electrons pass the anode cavities they tend to group due to the capacitance and inductance of the cavities formed by the fingers 46 and 49.

This grouping causes radio frequency induced current to fiow in the fingers and the frequency of this current is dependent among other things on the mode of operation of the tube. That is to say, that the electron grouping may excite a frequency which diifers from the basic mode of the system. The grouping may be considered analogous to the stroboscopic efiect wherein a different number of images occur at different modes.

Extending through the top cover IS at a position adjacent to the outer edge is an energy coupling means 5! which extends downwardly into the tube structure and connects to the upper anode 44. Energy is removed from the upper anode structure by this means. The energy coupling means 52, is insulated from and sealed to the cover 19.

I A second energy coupling means 53 is similarly attached to the bottom anode 48 and .removes energy from the lower system.

The outputs from the first and second energy coupling means may be used independently or may be connected in parallel. When they are connected in parallel, the resultant frequency is intermediate between the individual frequencies.

In order to obtain operation of the tube in a desired mode, the fingers of the anode structures may be strapped as shown in Figure 3. A plurality of straps 55 of a generally U shape have one end 51 connected adjacent the ends 56 of the fingers 46 and 49. The mid-portion 59 extends over the adjacent finger and the opposite end 58 is connected to the second finger. This is well shown in Figure 3. Any other well known method of strapping may, of course, be used.

Although this invention has been described with respect to a preferred embodiment thereof, it is not to be so limited since changes and modifications may be made therein which are within the full intended scope of the invention as defined by the appended claims.

I claim:

1. A magnetron tube comprising, a hollow cylindrical member, a first disc-shaped cover member received at one end of said cylindrical mem her, a first annular anode structure extending into said cylindrical member from said first cover member, a second disc-shaped cover member re ceived at the opposite end of said cylindrical member, a second annular anode structure extending into said cylindrical member from said second cover member, an annular cathode supported within said cylindrical member between said first and second anode structures with clearance therebetween, means for furnishing a direct current potential connected to said cathode and to said first and second anodes, magnetic field producing means for passing a magnetic field through the space between the cathode and the first and second anodes, said magnetic means comprising an external annular portion attached to said cylindrical member and an internal disc portion supported by one of said cover members, and means for removing energy from said tube attached to one of said cover members.

2. A magnetron tube comprising a hollow cylindrical member, a thin annular cathode adapted to radiate electrons from both sides thereof, a pair of supporting rings holding said cathode, fastening means concentrically attaching the supporting rings to the inner wall of said cylindrical member, a first disc-shaped anode member having a plurality of downwardly extending fingers, a second disc-shaped anode member having a plurality of upwardly extending fingers, said downwardly extending fingers received between said supporting rings and maintained in close proximity to said cathode, said upwardly extending fingers received between said supporting rings and maintained in close proximity to said cathode, magnetic means producing a field between said cathode and said first and second anodes, and comprising an external portion attached to said cylindrical member and an internal portion attached to one of said supporting rings, and a voltage source with the negative side connected to said cathode and the positive side connected to the first and second anodes.

3. In a magnetron according to claim 2 wherein said magnetic field producing means comprise, an inner thick disc formed with an axial opening and a plurality of smaller radial openings, a ring attached to the inner wall of said cylindrical member, flux conducting means external of said cylindrical member connecting said disc and said ring, and electrical means wound about said flux 5 means to produce a field between said disc and Number said ring. 2,437,279 PAUL I. CD-RBELL. 2,443,179 2,485,401 References Cited in the file of this patent 5 2 501 354 UNITED STATES PATENTS 2,504,

Number Name Date 2,071,311 Litlder Feb. 16, 1937 Number 2,084,867 PILIIZ et a1. June 22, 1937 515 229 10 2,411,953 Brown Dec. 3, 1946 Name Date Spencer Mar. 9, 1948 Benioff June 15, 1948 McArthur Oct. 18, 1949 Pease Mar. 21, 1950 Engelmann Apr. 25, 1950 FOREIGN PATENTS Country Date Great Britain Nov. 29, 1939 

